Calcium aluminate-supported catalysts are used in a number of industrial processes, including methanation and steam reforming processes, such as pre-reforming, primary reforming and secondary reforming. In such cases the catalytically-active metal is typically nickel, but other transition metals or precious metals, may also be used.
In methanation and steam reforming processes, pellets comprising nickel oxide on alumina or calcium aluminate are typically installed and the reduction of the nickel oxide to the active elemental nickel carried out in-situ.
U.S. Pat. No. 4,707,351 describes steam-reforming catalysts made of a low-silica calcium aluminate cement composition in a saddle configuration. The catalysts were prepared by mixing calcium aluminate with water and polyvinylacetate, stamping shapes from the resulting material, drying and calcining the saddles at up to 1400° C. before impregnation with nickel nitrate. The impregnated saddles were further dried and calcined to generate the catalyst precursor. In this process, the calcium aluminate support was hydrated during the shaping process and then calcined to increase its strength and define the micromimetric properties prior to impregnation with nickel nitrate.
Heretofore it has been seen as necessary to impregnate calcium aluminate supports to achieve a uniform dispersion of the metal compound within the pellets such that upon calcination the metal oxide is uniformly dispersed within the pellet, thereby maximising the metal surface area and hence catalyst activity.